The present invention relates to a process for producing a formed pitch-carbon product, more particularly to an improved infusibilizing process for producing a formed carbon product wherein a raw material pitch is prepared by mixing a pitch or a pitch precursor with a polymer and then by heat-treating the mixture.
In general, a formed carbon product is manufactured by forming a coal pitch, a petroleum pitch or a synthetic pitch and subsequently by infusibilizing and carbonizing the formed pitch product. In the manufacturing process, an infusibilizing step is so far the most time requiring step and has been a principal factor to lower the production efficiency of formed carbon products. In order to reduce the infusibilizing time, a variety of catalysts and accelerators have been investigated. For instance, in a method where a certain kind of metal salt was added to a pitch as a catalyst, although there were some salts showing recognizable effect on a reduction of an infusibilizing time, carbon products obtained have some deteriorated physical properties; and in an another method wherein the step was held in an atmosphere of halogen molecule or nitrogen oxide, which was thought to be an accelerator, although there was no carbon products having deteriorated physical properties, there was no significant reduction of time in the step. Accordingly, the methods so far investigated were unsatisfactory and it has been unavoidable to built a large scale infusibilizing apparatus because of its present ineffectiveness.
There are other infusibilizing methods, wherein pitch fibers are dusted with powdery solid lubricants such as molybdenum disulfide or talc and heat-treated thereafter and the methods are disclosed in Japanese Patent Application Laid-Open (KOKAI) Nos. 61-160,422(1986), 62-57,929(1987), 62-110,923(1987). These methods are effective in preventing fibers adhering together but almost no effect in reducing infusibilizing time.
As a result of extensive studies to develop a process for producing a carbon product, of which physical properties are not deteriorated, with a reduced infusibilizing time, the present inventors have found the fact that when a pitch or a pitch precursor (hereinafter referred to as "pitch et al.") is mixed with a polymer having no aromatic ring in each of the repeating unit, for example polyethylene; heated to make reaction with the polymer, further heated under reduced pressure to remove volatile components (hereinafter the heat-treatment to make reaction and the heat-treatment to remove volatile components are referred altogether in one word of "heat-treatment"); formed in an optional form; and infusibilized, there is no improvement of the infusibilizing time. On the other hand, the present inventors have further found the fact that when a pitch et al. is mixed with a certain polymer having an aromatic ring in each of the repeating unit, for example polyphenylene sulfide; heat-treated; formed; and infusibilized, the infusibilizing time is reduced remarkably and the carbonized products not only maintain the initial shape but also have physical properties not inferior to those of carbon products infusibilized for a long time and carbonized. Based on these findings, the present inventors have completed the present invention.